There were 96 cases of Staphylococcus aureus infection, including 68 cases (70.8%) in ALI group, of which 41 cases (60.3%) were positive in sputumculture and 27 cases (39.7%) were positive in blood culture. Compared with the non-ALI group, the proportion of patientsaged ≥60 years in ALI group was lower (58.8%(40/68) vs 64.3%(18/28)), the proportion of smoking was higher (58.8%(40/68) vs 35.7%(10/28)), and the differences were both statistically significant ( χ2=0.76 and 0.03, respectively, both P<0.05). The levels of CRP, PCT and NLR in the ALI group were all higher than those in non-ALI group, while oxygenation index and albumin level were both lower, and the differences were all statistically significant ( t=-5.28, -3.46, -9.87, 12.83 and 3.08, respectively, all P<0.05). Binary logistic regressionanalysis showed that CRP (odds ratio ( OR)=1.973, 95% confidence interval (95% CI) 0.956 to 2.989), PCT ( OR=3.734, 95% CI 1.014 to 13.746), NLR ( OR=1.152, 95% CI 1.058 to 2.254) and albumin ( OR=1.527, 95% CI 1.110 to 2.102) were independent risk factors for ALI caused by Staphylococcus aureus infection. The areas under the ROC curve of CRP, PCT, NLR, albumin and the riskwarning model constructed from the combination of four risk factors were 0.69, 0.81, 0.83, 0.78 and 0.93, respectively. The sensitivities were 65.14%, 89.91%, 84.40%, 56.88% and 98.17%, respectively. The specificities were 62.37%, 60.22%, 65.59%, 80.64% and 93.55%, respectively. The accuracy of the effectiveness test of the riskwarning model was 84.97%.